1. Field of the Invention
The present invention relates to an epoxy resin composition which is useful for adhesives, paints and electric/electronic materials(e.g. insulation materials, laminated plate, etc.), particularly useful for encapsulating electric devices.
2. Description of the Related Art
Recently, for encapsulating semiconductors such as LSI, IC, transistor and the like, transfer mold of an economically useful epoxy resin composition is conducted.
Particularly, surface mounting of LSI is recently conducted, and direct immersion into a solder bath is increasing. Since an encapsulating material is exposed to a high temperature of above 200.degree. C. in this treatment, moisture absorbed in the encapsulating material expands, crack is formed in the material, and peeling occurs at interface with a die pat.
Therefore, the epoxy resin encapsulant is required to have properties of low moisture absorption, high crack resistance and improved adhesion. Further, for a purpose of obtaining a low moisture absorption property, an epoxy resin of low viscosity in which a filler can be filled in high concentration is desired. Currently, an encapsulating material in which glycidyl ether of o-cresol novolak is used as a polyfunctional epoxy resin and phenol novolak is used as a curing agent is mainly used, however, when the encapsulating material absorbs moisture in storage, the above-described problems occur. Therefore, for avoiding these problems, the encapsulating material is wrapped for preventing moisture absorption in practical use.
On the other hand, a biphenyl type epoxy resin in current use has a lower viscosity and can contain a filler in higher concentration than a polyfunctional epoxy resin, since the biphenyl epoxy resin is a bifunctional epoxy resin and has a low molecular weight. Therefore, moisture absorption depending on the biphenyl type epoxy resin can be reduced as whole package and strength thereof can be increased, consequently, excellent crack resistance can be obtained as compared with an epoxy resin in the form of a glycidyl ether of o-cresol novolak. However, the biphenyl type epoxy resin has problem that molding property of a cured article thereof is low as compared with the polyfunctional epoxy resin.
Furthermore, the softening point of an amorphous epoxy resin having a low melt viscosity is generally low, and there have been problems of blocking at the time of storage to deteriorate the workability. Therefore, the amorphous resin is stored generally with cooling in a refrigerator, and the productive efficiency is bad and not economical.
There has been a proposal of using a bisphenol compound of .alpha.-methylstilbene as an encapsulating material (for example, JP-A-6-345849). However, the epoxy compound disclosed there is not sufficient in moldability etc.
An object of the present invention is to provide an epoxy resin composition which has an excellent moldability (low viscosity and can be filled with filler with high density) and high softening point, and hardly causes blocking during storage.